Boeing 737 Max airplanes sit parked at the company's production facility in Renton, Washington DC, the US on November 18. Photo: VCG

Boeing's 737 MAX is set to return to the skies in Canada with a local twist in the cockpit, after Ottawa became the last major Western regulator to lift a 20-month safety ban.

Small print in Thursday's Transport Canada announcement sheds light on a regulatory split over the use of a less common tactic to overcome cockpit distractions, deepening international disunity over the lessons from two fatal crashes.

Transport Canada joined the US Federal Aviation Administration and other regulators in requiring more training and revisions to MCAS anti-stall software implicated in the crashes in Indonesia and Ethiopia, which killed 346 people.

But unlike the FAA, Canada will give pilots an option to intervene in an electrical system to silence an alarm thought to have distracted crew as they tried to control the doomed jets.

In an unusual move, pilots in Canada will be allowed to pull a circuit-breaker or electric fuse to silence an erroneously activated "stick shaker," which vibrates the control column and makes a loud noise when the jet risks losing lift.

"Normally, pulling circuit breakers is considered an outdated practice and should only be done when directed by a checklist and not as a method of troubleshooting," said Tim Perry, president of Air Line Pilots Association (ALPA) Canada.

Perry said he backs Canada's procedure: "Upon thorough evaluation, we deemed it safe."

The two MAX crashes, involving a computer that pushed the nose down because of false flight data, had already undermined decades of efforts to harmonize safety rules as regulators worldwide banned the jet without waiting for the FAA.

The Canadian push to let pilots pull a circuit-breaker is further proof of regulators' willingness to check each other's homework and could increase pressure to be heard from pilots.

"The more differing viewpoints you have, the more of a problem it is for industry," said Michael Daniel, a former FAA certification expert.

Transport Canada, a low-key figure in a field dominated by heavyweights in the US and Europe, said it had spent over 15,000 hours reviewing the MAX. Like its European counterpart, it is unwilling to surrender its increased role.

"Canada will absolutely have a greater involvement in... either independent testing throughout the validation process, or a greater engagement in the actual testing itself," Nicholas Robinson, its head of civil aviation, told Reuters.

Steering clear



Pilots, who played an important part in MAX discussions, also want a permanent say in future approvals.

"The extensive return-to-service exercise illustrates the need to have airline pilots involved in the certification process," said Perry.

The delicate role of cockpit fuses surfaced in 2014 when an Indonesia AirAsia captain appeared to pull a fuse linked to a malfunctioning computer before his Airbus jet crashed, investigators said. 

French and Indonesian investigators disagreed over how far that went against the manual.

In a Boeing study of stick-shaker alarms on 737s since 2001, cited in the official report on the first 737 MAX crash in 2018, crew had pulled a breaker in one out of 27 such incidents.

While not common, Robinson said there are cases where pilots pull breakers. He said it's better to act with an established procedure, like Canada's new rule, than to react on the spot.

"In some cases, the only way to cancel the warning is to pull the circuit breaker," said US aviation training expert Kit Darby. "It's like someone blaring their horn at you."

As discussions over the 737 MAX grounding wore on, Europe's regulator and pilot unions backed Canada's plan.

The European Union Aviation Safety Agency ordered a colored cap on the circuit breaker to help find it.

The FAA refused to follow suit, saying pilots would not be able to reach the right fuse with seat-belts properly fastened.

It publicly raised concerns that trying to reach behind for the fuse panel would distract pilots from primary duties and could result in accidentally pulling the wrong fuse.

Pilots at US budget carrier Southwest Airlines have backed the Canadian move and urged the FAA to adopt it.